Construct flag emoji from ISO 3166-1 2 letter country code

flag.js

/*
 * Constructs an emoji flag using a supported ISO 3166-1 2 letter country code.
 * 
 * Per character in the input string it shifts it 127365 code points from the ASCII lower case 
 * characters to Regional Indicator Symbol series, which is used to construct flag emoji.
 * 
 * @param {String} regionCode   String starting with a supported ISO 3166-1 2 letter region code.
 * @returns {String}            Emoji flag character constructed from 2 regional indicator symbols.
 */
function flag(regionCode = '') {
    return regionCode.toLowerCase().split('', 2).reduce((m, char) => {
        return m + String.fromCodePoint(char.codePointAt(0) + 127365)
    }, '')
}